Telegraphone.



No. 890,195. PATENTED JUNE 9, 1908. H. R. STUART.

TELEGRAPHONE.

APPLICATION rum) SEPT.Z4,1907.

2 SHEETS-SHEET 1.

Fq'g. 1.

r PATENTED JUNE 9, 1908. H. R. STUART.

TBLBGRAPHONB.

APPLI OATION FILED SEPT. 24. 1907.

2 SHEETS-SHEET 2.

5 mm W606 M f 33n LL. 611mm wi/mwoeo $6 0M near the center where it is slow.

STATES PATEnr onnron.

HARVE R. STUART, or WHEELING, wEs'r VIRGINIA.

'rnnnenarnonnl 'citizen' of the United States, residing \at Wheeling, in the county of Ohio and State of West Vir 7 'a, have lnvented certain new.

and usefu Im rovements in Telegraphones, of which the ollowing is a full, clear, and exact description.

My invention relates to apparatus for magnetically recording and reproducing sound and commonly known as the telegraphone, and more particularly to what is termed a disk machine in which a circular steel plate or disk revolves on its ownaxis in close proximity or contact with a recording and reproducing magnet which moves radially with respect to the disk and traces a spiral path thereon.

In a disk telegraphone of this type, it is evident that there is a reater linea speed of the material of the dis with respect to the recording and reproducing magnet when said magnet is near the circumference than when it is near the center of the disk (assuming the speed of rotation of the disk is constant.) This fact tends to produce a much louder reproduction near the circumference of the disk where the lineal movement is rapid than In order to correct this tendency, it has been proposed to continuously vary the speed of rotation of the disk. By the present invention, I com- I pensate for the variation of lineal speed relation occurring as mentioned in another and special way which is found to be very efficient coming the tendency or difiiculty mentioned, and capable of being embodied in very compact and eflicient mechanical form.

The essential rinciple on which the present invention is ased depends upon the fact that in telegraphone apparatus the loudness or efficiency of reproduction is greater in pro- .portion to the wldth of the pole face of the recording and reproducing magnet, and the corresponding width of the magnetic path on thev recordin and reproducing medium. I have found t at this efiiciency or loudness of re roduction varies almost directly with the width of the pole face. As the loudness or efficiency of reproduction also varies in direct proportion to the linealspeed relation between the pole face and the recording medium, I pro ose to take-advantage of the first-named act or principle to compensate Specification of Letters Patent.

Application filed September 24, 1907. Serial No. 394,293.

.and reproducing magnet.

Patented June 9, 1908.

for the result produced by the last-named fact or principle in a disk machine.

My invention therefore consists in the features of construction and combination as hereinafter set forth and claimed, by-w-hich m the foregoing princi les are utilized.

In the drawings, igure 1 is a top or plan view showing a telegraphone record disk and the recording and reproducing magnet therefor, together with certain parts embodying the principles ofmy invention, by which their proper relative movement is obtained. Fig. 2 is a side elevation of the same. Fig. 3 isa detail sectional view.

Referring to the drawings in which like parts are designated by the same reference sign, 1 indicates a box or casing which constitutes the main frame or support for all the operating parts.

2 indicates a s indle projecting upward from the base 1, eing revoluble in journal bearings 3 and 4 thereon.

5 indicates a motor of any ordinary sort for imparting a continuous rotation to the spindle 2. I have illustrated a device 6 by which a record disk 7 may be placed upon and rotated with the spindle 2 in coaxial relation. These features for supporting and rotating the record disk may, of course, be of any suitable or desired nature.

There is rovided a vertical shaft 8 in fixed and parallel relation to the axis of the spindle 2. About the shaft 8 as an axis there swings an arm 9 carrying the recording and reproducing magnet 10, which projects from the 90 arm 9 into close proximity or contact with the disk 7. It is evident that the distance of the axis 8 from the spindle 6, and the distance of the pole of the recording and reproducing magnet from said axis 8 are factors which ma be varied, and which when varied cause di erent relations between the disk and the path of movement of the recording These two factors are, however, the only ones which effect 1 said relations, and the determination of these two factors is therefore alone sufficient to obtain any particular desired result.

In practice, I prefer that the recording and reproducing medium shall move in an almost radial direction when near the center of the disk, but when approaching the circumference that the movement should become more and more tangential. Also, (and I regard this as a very important feature of the inven- 10 Fig. 1.

tion) that the pole face of the recording and reproducing magnet should be displaced through an angle of about 90 with respect to its magnetic path on the disk in passing 5 from the center to the circumference of the disk or vice-versa. With these relations I form the pole face of the recording and reproducing magnet considerably elongated in one direction in the manner shown at in I then fix the recording and reproducing magnet upon the supporting arm 9,

so that the pole face 10 lies squarely across the movement of the disk when at its inner position thereon. Under these circumstances, the pole face presents its narrowest width to the movement of the disk when the magnet is at its outer position, on account of the angular displacement of the pole face occurring as mentioned. While 1 have indi- 2'0 cated this particular manner of supporting and guiding the recording and reproducing magnet with relation to the disk so as to obtain a 90 displacement of the pole face with respect to the magnetic path when moving from the center to the circumference of the disk, I do not desire to be limited or restricted thereto, since it is evident that other equivalent mechanisms may be used in lieu thereof for accomplishing the same purpose.

I consider the form shown as a desired practical construction, however, because it not only secures the 90 displacement of the elongated pole face with respect to the magnetic path in passing from the center to the.

circumference of the disk and vice-versa, but

also causes a rather more rapid radial movement ofthe recording and reproducing magnet at the center of the disk than atthe circumference, on account of the increasingly tangential character of the movement. It is evident that if the arm 9 swings with a constant or unvarying s eed from the circumference inward towar s the center of the disk, that it will trace coarser spirals near the center than near the circumference, and this is desirable because the magnetic path traced by the pole face at the center of the disk is wider than that traced I near the circumference. The mechanism for causing the arm 9 to swing in and out when the disk rotates, may be of any suitable sort. I have shown a practical construction including a cam 11 engaging a roller or protuberance 12 projectin'g upward from the end of an arm 13 rigid with the arm 9.

14 indicates a spring acting to bear the roller or protuberance 12 against the face of the cam 11.

15-and 16 indicate gears or reducing mechanism by which the cam is rotated slowly,

while the disk 7 spins on its axis 2. In practice, a clutch 17 0f any suitable form may be interposed between the gear 16 and the cam 11, so that the cam may be set by hand at different angular positions without disturbing the disk 7. For the purposes of illustration, I have shown a thumb-wheel 18 by which the cam can be turned in this way independently of the gear 16. It is to be noted 7 that the clutch 17 should have a definite relation to the reducing value of the gear train between the spindle 2 and the cam 11. The clutch should have a number of positions of engagement which is an exact divisor of said. reducing ratio. For example, if the cam 11 makes one revolution for 1000 revolutions of the disk 7, the clutch 17 may have ten or' twenty engaging positions, or any other number which is an exact divisor of 1000. 3a Twelve or fifteen engaging positions of the clutch 17 would not answer, because these numbers are not an exact divisor of 1000 in the example mentioned. With the latter figures, the recording and reproducing mag- 35 net would. not necessarily trace the same path after the cam had been shifted and the clutch 17 rengaged by a new position, as before.

In operation, the disk 7 rotates continuously and uniformly under the influence of v the motor 5, and the cam 11 rotates very slowly through its reducing connections with the disk. The arm 9 carrying the recording and reproducing magnet has its position at all times determined by the angular position of the cam on account of its arm 13 carrying stud or roller 12 which constantly bears against saidcam. The cam being made of general spiral form as shown in the figure, it is evident that the arm 9 and therecording and reproducing magnet swing from the circumference to the center of the disk or viceversa as the cam completes a single revolution. In order to return the magnet to its starting position, or in order to re-trace any portion of the record disk, it is merely necessary to shift the position of the cam through the clutch 17 by the thumb-wheel 18, or any other similar or equivalent mechanism desired. 1

It is evident that the form of the cam may be made in any way desired so as to get any particular constant or varying pitch or feed of the recording and reproducing magnet in its inward and outward movement.

What I claim, is:

1. In combination with a recording and reproducing medium mounted to have a greater lineal movement at some portions of its surface than atothers, a magnet having an elongated pole face cooperating with the said medium, and means for angularly displacing said pole face with respect to the direction of movement of the medium in passing from ortions of one velocity of movement to t ose of another.

2. In a telegraphone, a rotatable disk, a recording and re roducing magnet having an elongated pole ace, and means for moving said magnet from the circumference to the position than in another, means for moving thereof, said the magnet over the face of the disk as the disk rotates, and means for displacing said pole face angularly during such movement.

5. In a telegraplione, a uniformly rotating disk, a ma net movable over the surface magnet having an elongated pole face, and means for angularly displacing said ole face during said movement.

6. n a telegraphone, a rotatable disk, an

arm swinging on a fixed axis across the face of said disk, and a magnet carried by said arm and having an elongated pole face presented to the disk.

7. In a telegraphone, a rotatable disk, an arm swinging on a fixed axis across the face of said disk, and a magnet carried by said arm and having an elongated pole face presented to the disk, said pole face occupying a position with its long dimension squarely across the direction of its magnetic path on the disk when at a position near the center thereof.

8. In a telegraphone, a rotatable disk, and a magnet swinging on a fixed axis across the face of said disk and adapted to trace a spiral magnetic path thereon, the swinging movement of said magnet being more nearly radial at a position near the center of the disk than at the circumference.

9. In a telegraphone, a rotatable disk, a magnet pivoted on a fixed axis and movable over the face of said disk, and means actuated by the rotation of the disk for swinging said magnet on said axis.

10. I11 a .telegraphone, a rotatable disk, a v

magnet having an elongated )ole face, said magnetbeing pivoted on a ixed axis and movable over the face of said disk, and means actuated by the rotation of the disk for swinging said magnet on said axis.

11. In a telegraphone, a rotatable disk, a magnet having an elongated pole face with its long dimension squarely across its magnetic path on the disk when at a position near the center thereof, said magnet being pivoted on a fixed axis and movable over the face of said disk, and means actuated by the rotation of the disk for swinging said magnet on said axis.

12. In a telegraphone, a rotatable disk, a v

magnet swinging on an axis across the face.

of said disk and adapted to trace a wider magnetic path near the center than near the circumference thereof, and a cam connected to rotate with said disk and acting to swing said arm on said axis.

In witness whereof, I subscribe my signature, in the presence of two witnesses.

, HARVE R. STUART.

Witnesses WM. D. CooKE, LOUIS WALTERS. 

